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[209.132.180.67]) by mx.google.com with ESMTP id m6si22308722pgp.423.2019.07.31.15.21.27; Wed, 31 Jul 2019 15:21:42 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=FZCV7mLb; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730327AbfGaWRj (ORCPT + 99 others); Wed, 31 Jul 2019 18:17:39 -0400 Received: from mail-vk1-f202.google.com ([209.85.221.202]:51179 "EHLO mail-vk1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731418AbfGaWRg (ORCPT ); Wed, 31 Jul 2019 18:17:36 -0400 Received: by mail-vk1-f202.google.com with SMTP id p196so29966985vke.17 for ; Wed, 31 Jul 2019 15:17:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=lAGo2XEfN1Kmsxc7Q91nfXTi8fMC4u4EK30rK7PWIbE=; b=FZCV7mLbwgIyfiHg2Uw26K8PzqMs/1VlHh76kTcAH9mnfXS7n/oSsgvblYsFl5auM4 mBOEFvy28hQLGkmT1c4BZLYH7v0L6tIeCyxfgskIB9st8ur99CzAHj8VpYbqEbfSOcgl oNMJxPh+CGcNjgIEiDCLThuyt+DuYEJYYzkozB83eyoL4EAUcqzDzyngBZUHN+Ek+/PA fUKYK3gyCrm+tV2dSghSL+ScFBI8kxrLV4nzm9O9pD8hvu++Msi8X++zQZPaeQ3nJIkA h1/DwalZk7aHIIyrFM19hqg0RzU6W9pRu+1CCfgn8mlcEsjj1T68cKwEyFLcPECS5+Le q39Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=lAGo2XEfN1Kmsxc7Q91nfXTi8fMC4u4EK30rK7PWIbE=; b=tL86VRA59UxVYv3LwzQxPyweJWfY58NgRC9icyVZv9Y6lepEkzlqyHS8L2AH0H2dKQ GNAZQVRau/IhIbp9a0npwlh+q8En1uTQ2zvAOkn0Re+LLr08flphtUGjtr5HFblsC6D6 bZCc6qeLZY2ZDKtJGsb1IdI6TIztbzWuGOvSkbJnhlcGqjiVtWadHjvgYD7SQDJLsjC8 jVyRx2+87vAM+eOBzJhGe0ipzLr+Y+yivbLJ+7s2M5+SpM7rgxH6ufrpvMC1e7Rtpw+J qovsJZk+F83aDhbvMTK/0O40Y/AKoTUvpReINxu1dgWbGI+cy/u92ovjWXocfYJaZYvr Fkxg== X-Gm-Message-State: APjAAAWIiCnyA5ElCHAPf9wRZTPjsmJ5VD9+F1JvW8b9d63EYPe8OE66 6HbD3ZuPzVRKJY2hsHMGcFSNIeruPmhrhEm0knt85Q== X-Received: by 2002:a67:f1d6:: with SMTP id v22mr78230446vsm.178.1564611455461; Wed, 31 Jul 2019 15:17:35 -0700 (PDT) Date: Wed, 31 Jul 2019 15:16:15 -0700 In-Reply-To: <20190731221617.234725-1-matthewgarrett@google.com> Message-Id: <20190731221617.234725-28-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190731221617.234725-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.22.0.770.g0f2c4a37fd-goog Subject: [PATCH V37 27/29] tracefs: Restrict tracefs when the kernel is locked down From: Matthew Garrett To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Matthew Garrett , Matthew Garrett , Steven Rostedt Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Tracefs may release more information about the kernel than desirable, so restrict it when the kernel is locked down in confidentiality mode by preventing open(). Signed-off-by: Matthew Garrett Reviewed-by: Steven Rostedt (VMware) --- fs/tracefs/inode.c | 40 +++++++++++++++++++++++++++++++++++- include/linux/security.h | 1 + security/lockdown/lockdown.c | 1 + 3 files changed, 41 insertions(+), 1 deletion(-) diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c index 1387bcd96a79..12a325fb4cbd 100644 --- a/fs/tracefs/inode.c +++ b/fs/tracefs/inode.c @@ -21,6 +21,7 @@ #include #include #include +#include #define TRACEFS_DEFAULT_MODE 0700 @@ -28,6 +29,23 @@ static struct vfsmount *tracefs_mount; static int tracefs_mount_count; static bool tracefs_registered; +static int default_open_file(struct inode *inode, struct file *filp) +{ + struct dentry *dentry = filp->f_path.dentry; + struct file_operations *real_fops; + int ret; + + if (!dentry) + return -EINVAL; + + ret = security_locked_down(LOCKDOWN_TRACEFS); + if (ret) + return ret; + + real_fops = dentry->d_fsdata; + return real_fops->open(inode, filp); +} + static ssize_t default_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos) { @@ -210,6 +228,12 @@ static int tracefs_apply_options(struct super_block *sb) return 0; } +static void tracefs_destroy_inode(struct inode *inode) +{ + if (S_ISREG(inode->i_mode)) + kfree(inode->i_fop); +} + static int tracefs_reconfigure(struct fs_context *fc) { struct super_block *sb = fc->root->d_sb; @@ -236,6 +260,7 @@ static int tracefs_show_options(struct seq_file *m, struct dentry *root) static const struct super_operations tracefs_super_operations = { .statfs = simple_statfs, + .destroy_inode = tracefs_destroy_inode, .show_options = tracefs_show_options, }; @@ -372,6 +397,7 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode, struct dentry *parent, void *data, const struct file_operations *fops) { + struct file_operations *proxy_fops; struct dentry *dentry; struct inode *inode; @@ -387,8 +413,20 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode, if (unlikely(!inode)) return failed_creating(dentry); + proxy_fops = kzalloc(sizeof(struct file_operations), GFP_KERNEL); + if (unlikely(!proxy_fops)) { + iput(inode); + return failed_creating(dentry); + } + + if (!fops) + fops = &tracefs_file_operations; + + dentry->d_fsdata = (void *)fops; + memcpy(proxy_fops, fops, sizeof(*proxy_fops)); + proxy_fops->open = default_open_file; inode->i_mode = mode; - inode->i_fop = fops ? fops : &tracefs_file_operations; + inode->i_fop = proxy_fops; inode->i_private = data; d_instantiate(dentry, inode); fsnotify_create(dentry->d_parent->d_inode, dentry); diff --git a/include/linux/security.h b/include/linux/security.h index d92323b44a3f..807dc0d24982 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -121,6 +121,7 @@ enum lockdown_reason { LOCKDOWN_KPROBES, LOCKDOWN_BPF_READ, LOCKDOWN_PERF, + LOCKDOWN_TRACEFS, LOCKDOWN_CONFIDENTIALITY_MAX, }; diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c index 88064ce1c844..173191562047 100644 --- a/security/lockdown/lockdown.c +++ b/security/lockdown/lockdown.c @@ -36,6 +36,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { [LOCKDOWN_KPROBES] = "use of kprobes", [LOCKDOWN_BPF_READ] = "use of bpf to read kernel RAM", [LOCKDOWN_PERF] = "unsafe use of perf", + [LOCKDOWN_TRACEFS] = "use of tracefs", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", }; -- 2.22.0.770.g0f2c4a37fd-goog